Dresden 2009 – scientific programme
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DS: Fachverband Dünne Schichten
DS 16: Poster I
DS 16.10: Poster
Tuesday, March 24, 2009, 09:30–12:30, P5
Highly efficient organic blue light emitting devices using doped transport layers — •Nico Seidler1, Sebastian Reineke1, Karsten Walzer1, Björn Lüssem1, Ausra Tomkeviciene2, Juozas V. Grazulevicius2, and Karl Leo1 — 1Institut für Angewandte Physik / Photophysik, Technische Universität Dresden, D-01062 Dresden — 2Department of Organic Technology, Kaunas University of Technology, Kaunas LT-50254, Lithuania
In contrast to red and green OLEDs, blue light emitting devices are still far away from the theoretical limit of about 20 % external quantum efficiency. The best results so far have been achieved involving ultrahigh energy gap organosilicon compounds [1]. Due to their poor transport properties, high efficiencies are obtained only at low current densities and high voltages.
We used the blue phosphorescent emitter iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) as a dopant in the host material 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole, which possesses both a large triplet exciton energy and good charge carrier transport properties. It was therewith possible to efficiently confine the triplet excitons on the emitting molecules and keep the recombination zone away from the blocking layers. This results in a high external quantum efficiency of 13.1 % at a brightness of 1,000 cd/m2. Due to the superior charge carrier injection properties provided by the doped transport layers, this brightness could be achieved at low voltages of only 4.0 V, resulting in a high power efficiency of 22.5 lm/W.
[1] X. Ren et al., Chem. Mater. 16, 4743 (2004)